1. Field of the Invention
The present invention relates generally to a zoom lens which is used with a camera or a digital video camera, and more particularly to a lens retraction mechanism of the zoom lens and the retracting method of the same.
2. Description of the Prior Art
In recent years, most photographic devices, such as digital cameras or digital video cameras, are equipped with zoom lenses. Users can photograph objects in different distances with one device by extending or retracting the zoom lens to adjust the lens focus. In shooting a distant object, the photographic device must have the lens extended by a zoom multiple. The larger the zoom multiple is, the longer the extended lens is. Users usually do not care about how long the lens can be extended in taking photographs, but they are more concerned about the overall weight and size of the photographic device when the lens of the device is retracted to a nonuse state.
FIG. 1 of the attached drawings shows a conventional lens retraction mechanism of a zoom lens. The conventional zoom lens comprises a lens barrel 9 and first, second and third lens groups 91, 92, 93 received in the lens barrel 9. The lens groups 91, 92, 93 are sequentially and respectively received in a receiving space along an optical axis Z0. In the conventional retraction arrangement, the lens thickness inevitably exceeds the sum of the thickness of all lens groups 91, 92, 93. Accordingly, the overall thickness of the photographic device is not satisfactory for general consumers.
In order to reduce the lens thickness, methods have been employed to retract the lens groups by deviating the lens away from the optical axis of the photographic device and retraction mechanisms working in this way are available in the market. An example is Ricoh Caplio R1 digital camera, in which when the lens begins to retract, a front lens group of the lens is drawn back along an optical axis of the lens, while a rear lens group of the lens is moved away from the optical axis, and finally positioned in either side space of the optical axis, to leave a space for accommodating backward moved front lens group. This arrangement allows the multiple lens groups to be stowed without stacking over each, and instead sideways positioned side by side, so as to reduce the overall thickness of the lens in a stowed condition.
Another example of lens retraction by sideways deviating lens from the optical axis is Pentax Optio S50 digital camera. When power supply is shut off, the lens is sequentially drawn back into the camera body, while a central lens group is moved upward, in a direction transverse to an optical axis of the lens, so as to leave a space for front and rear lens groups which are moved along the optical axis.
Such retraction structures and methods can also refer to the Japanese Patent Application Nos. 2004-317943, 2004-361657, 2004-361921, and US Patent Application Serial No. 20040228626.
The US Patent Application discloses a lens retraction mechanism for driving a lens barrel to move between an advanced state and a retracted state. The lens barrel comprises a front lens group, a rear lens group, and a focusing lens group. When the lens barrel is moved from the advanced state to the retracted state, the lens retraction mechanism moves at least one lens group sideways away from an optical axis to a receiving space sideways deviating from the optical axis; and when the lens barrel is moved from the retracted state to the advanced state, the lens retraction mechanism moves the sideways-deviated lens group back to the optical axis. The lens retraction mechanism comprises a stepping motor, and when the lens barrel starts to retract, a driving gear coupled to the stepping motor rotates at a predetermined timing and with this, a transmitting gear fixed to a rear lens group holding frame is forced to rotate and fiber transmitting its rotation force to a receiving gear. Therefore, the rear lens group is retracted with the rotation and retraction of the rear lens group holding frame, from the optical axis to the retracted state which is deviated from the optical axis. However, this known lens retraction mechanism has a complicated structure because it uses a lot of gears, which need to precisely mate each other and rotate synchronously. If one gear goes wrong, the whole lens retraction mechanism fails to work. Furthermore, in the retraction of the rear lens group, the rear lens group holding frame retracts by way of rotation, which increases the movement path of the rear lens group from the advanced state to the retracted state, thereby costing a lot of retraction time of the rear lens group.
Hence, an improved lens retraction mechanism and method for the mechanism are desired to overcome the above-mentioned disadvantages of the prior art.